This invention relates to thermally curable compositions. More particularly, this invention relates to thermally curable polyacrylate compositions.
Polyacrylates have been employed extensively in the formulation of radiation curable coatings. Generally, such radiation curable coating compositions are formulated on a 100%, or close to 100%, basis, i.e., very little or no inert volatile solvents are present. When such coatings are applied and cured, no volatile solvents need to be recovered or vented to the atmosphere, thereby reducing or eliminating environmental pollution concerns. Attempts have been made to use radiation curable coatings compositions in thermally curable systems in order to take advantage of the absence of solvents. However, the use of such polyacrylates in non-radiation curable coating applications has been extremely limited because polyacrylates, in many cases, do not cure in thin films by thermal free radical initiation due to extreme oxygen inhibition. High baking temperatures and long baking times are needed in order to obtain good cured films.
A modified polyacrylate composition that can be cured by radiation is described in U.S. Pat. No. 4,434,278. These modified polyacrylates are acrylic acid esters-phosphoric acid esters of diepoxides made by reacting acrylic acid and phosphoric acid with the diepoxide compound. There is no disclosure in the patent that such phosphate ester compositions will thermally cure.
U.S. Pat. No. 4,026,826 discloses curable compositions that are used as anti-fogging, abrasion resistant coatings. The curable compositions are comprised of a blend of a hydrolysate of a silicon compound which serves to improve abrasion resistance, and a polymerizable acrylate which serves as an anti-foggent. The hydrolysate of the silicon compound is cured by a condensation reaction through the hydroxyl groups using a curing catalyst, such as phosphoric acid or cobalt naphthenate. The acrylate is polymerized by any suitable means, such as by heating the mixture in the presence of a radical polymerization catalyst or irradiating it with ionizing radiation.
It is an object of this invention to prepare thermally curable polyacrylate compositions.
It is another object of this invention to prepare polyacrylate compositions that can be thermally cured to a tack-free film on metal substrates.
These and other objectives are obtained by preparing the compositions of the instant invention.